While some people seem to be able to eat what they want, others struggle with their weight, no
matter what diet they try. A new study the Weizmann Institute in Rehovot, Israel, led by Prof Eran Segal and
Dr Eran Elinav is looking at the role of gut bacteria.
Nearly 1000 people filled in detailed health and medical data before taking part in a week-long study of how their blood sugar
levels reacted to different foods. During the week, their blood
sugar levels were measured constantly by a glucometer placed under the
skin, their sleep and activity levels monitored by a wrist-band, and
they were given an app to record their mood, feelings, sleep and exercise
regimes and what they ate. Throughout the week, their meals were
planned: some are standard foods that everyone tries, while others they can choose, but they had to weigh it all
accurately, and record it in precise detail. Each person in the
study has also given a stool (poo) sample. From this, the researchers
analyse the gut bacteria living inside each person. Our gut bacteria
are unique to us – it is almost like a ‘fingerprint’ of a person – but,
crucially, they can change.
The researchers at the Institute have found several startling things during their study:
Firstly, every person reacts differently to specific foods. This contradicts the theory that some foods give everyone a sudden blood sugar ‘spike’ while other foods give less of a spike - the high GI or low GI rating - but up till now these foods have only been tested on a standard group of 12 people.
The researchers at the Institute have found several startling things during their study:
Firstly, every person reacts differently to specific foods. This contradicts the theory that some foods give everyone a sudden blood sugar ‘spike’ while other foods give less of a spike - the high GI or low GI rating - but up till now these foods have only been tested on a standard group of 12 people.
Secondly, the huge amounts of data mean the team could make firm links between a person’s individual response to food, and to
the gut bacteria that they have. They have developed a computer
algorithm that can take a person’s individual gut bacteria
composition, and from it, predict how their blood sugar levels will
react to a whole range of foods.
Thirdly, in a small study 25 people had a ‘good’ and ‘bad’ diet predicted for each of them by the algorithm. They ate only the ‘good’ for one week and then the ‘bad’ for another – without knowing which was which. Their blood sugar reacted as predicted to the different foods, but there were also changes in their gut bacteria over just the week. The changes seen in the 'good' food week appeared to be beneficial. So we may be able to personalise our diets for health and and may be able to change our responses to food.
Dr Saleyha Ahsan of Trust Me, I'm a Doctor took part in the study. Foods that were found to be good for Saleyha’s blood sugar levels included: avocado, croissant, yoghurt & granola, banana & walnuts, omelette, chocolate, ice cream & cola. Foods that were found to be bad for Saleyha’s blood sugar levels included: grapes, cereal with milk, pizza, pasta, tomato soup, chicken sandwich (on wholemeal bread), orange juice and sushi. These are very individual to Saleyha.
Another volunteer of the same age and sex, eating the same meals alongside Saleyha for the week had the opposite blood sugar reaction to pizza, pasta, banana & nuts, yoghurt & granola and croissant. They also responded in the opposite way to white bread, and white bread with butter.
Saleyha then spent two weeks of eating only the foods identified as ‘good’ and avoiding the ‘bad’. In just this short time, her gut bacteria changed – and some of those changes were associated with a more ‘beneficial’ gut microbe composition. This short and uncontrolled trial did fit with the results the team saw in their own controlled trials of a similar diet.
Feature on Trust Me, I'm a Doctor, BBC2 on 27 Jan. 2016
Thirdly, in a small study 25 people had a ‘good’ and ‘bad’ diet predicted for each of them by the algorithm. They ate only the ‘good’ for one week and then the ‘bad’ for another – without knowing which was which. Their blood sugar reacted as predicted to the different foods, but there were also changes in their gut bacteria over just the week. The changes seen in the 'good' food week appeared to be beneficial. So we may be able to personalise our diets for health and and may be able to change our responses to food.
Dr Saleyha Ahsan of Trust Me, I'm a Doctor took part in the study. Foods that were found to be good for Saleyha’s blood sugar levels included: avocado, croissant, yoghurt & granola, banana & walnuts, omelette, chocolate, ice cream & cola. Foods that were found to be bad for Saleyha’s blood sugar levels included: grapes, cereal with milk, pizza, pasta, tomato soup, chicken sandwich (on wholemeal bread), orange juice and sushi. These are very individual to Saleyha.
Another volunteer of the same age and sex, eating the same meals alongside Saleyha for the week had the opposite blood sugar reaction to pizza, pasta, banana & nuts, yoghurt & granola and croissant. They also responded in the opposite way to white bread, and white bread with butter.
Saleyha then spent two weeks of eating only the foods identified as ‘good’ and avoiding the ‘bad’. In just this short time, her gut bacteria changed – and some of those changes were associated with a more ‘beneficial’ gut microbe composition. This short and uncontrolled trial did fit with the results the team saw in their own controlled trials of a similar diet.
The team hope that they will in the
future be able to take stool samples, sent through the post, and provide
a personalised diet plan in return – listing foods predicted
to give that person an unhealthy blood sugar spike, and those likely to maintain more stable, healthy blood sugar levels. These
will, of course, have to be eaten within a normally balanced diet – it
doesn’t mean that if chocolate turns out to be on your ‘good food’ list,
you can live on it and be healthy! The fact that ‘good’
foods for particular individuals usually seem to include some that
people very much like, means that such personalised diets would be
easier for people to adopt than traditional restrictive ones.
The team are also now studying the longer-term effects of diet on gut bacteria. It is possible that as the gut bacteria change in response to the diet (which happens within days or weeks), that the diet could then be modified, or relaxed.
The team are also now studying the longer-term effects of diet on gut bacteria. It is possible that as the gut bacteria change in response to the diet (which happens within days or weeks), that the diet could then be modified, or relaxed.
Feature on Trust Me, I'm a Doctor, BBC2 on 27 Jan. 2016
